QUANTIFICATION OF MAGNETIC FORCE MICROSCOPY USING A MICRONSCALE CURRENT RING

Metal rings with inner diameters of 1 and 5 mu m, fabricated using ele ctron-beam lithography, were used to calibrate magnetic force microsco py (MFM). A MFM tip's effective magnetic charge, q, and effective magn etic moment along the tip's long axis, m(z), can be determined from th e MFM signal of the ring at a different scan height and a different el ectric current in the ring. The magnetic moments in the directions tra nsverse to the tip's long axis were estimated by a straight current wi re. It was found that for a Si tip coated with 65 nm cobalt on one sid e, q is 2.8X10(-6) emu/cm, m(z) is 3.8X10(-9) emu, and m(x) and m(y) a re in the order of 10(-13) emu, which are negligible compared with m(z ). Furthermore, the MFMs sensitivity to the second derivative of the m agnetic field was determined from the minimum ring current for a measu rable MFM signal to be 0.1 Oe/nm(2). (C) 1997 American Institute of Ph ysics.